Tell me what it's like to ride a subway?

There's a constant rumbling sound. The wheels and tracks are metal, so you hear a screeching metallic sound when the train stops and the hiss of the hydraulics when it starts to move. The Europeans tend to use rubber wheels to reduce the noise, but American cities don't bother - they're expensive and cold weather destroys them. The seats tend to be plastic benches. Colors vary from city to city. SF's use a lot of light blue, Boston's lines are color-coded (Blue, Gree, Orange, Red and Silver), NYC and Chicago use a lot of red/orange (though I could be a little off, it's been a while).